Vein thrombosis is a medical condition wherein a blood clot, or thrombus, has formed inside a vein. Such a clot often develops in the calves, legs, or lower abdomen, but can also affect other veins in the body. The clot may partially or completely block blood flow, and may break off and travel through the bloodstream. Commonly, the clot is caused by a pooling of blood in the vein, often when an individual is bed-ridden for an abnormally long duration of time, for example, when resting following surgery or suffering from a debilitating illness, such as a heart attack or traumatic injury. However, there are many other situations that cause the formation of a blood clot.
Vein thrombosis is a serious problem because of the danger that the clot may break off and travel through the bloodstream to the lungs, causing a pulmonary embolism. This is similar to a blockage of the blood supply to the lungs that causes severe hypoxia and cardiac failure, and frequently results in death. For many patients, anti-coagulant drug therapies may be sufficient to dissipate the clots. For example, patients may be treated with anticoagulants such as heparin and with thrombolytic agents such as streptokinase.
Unfortunately, some patients may not respond to such drug therapy or may not tolerate such therapy. Also, there may be other reasons why an anticoagulant is not desirable. For example, patients may have an acute sensitivity to heparin or may suffer from prolonged internal and/or external bleeding as a result of such drug therapies. Also, such drug therapies simply may be ineffective in preventing recurrent pulmonary emboli. In such circumstances, surgical procedures are required to prevent pulmonary emboli. One current standard of therapy for prevention of pulmonary emboli in patients who are classified high-risk or are unable to be anticoagulated is percutaneous insertion and placement of an inferior vena cava filter device.
Vena cava filters are devices which are implanted, usually in the inferior vena cava, providing a mechanical barrier to undesirable particulates. The filters may be used to filter peripheral venous blood clots and other particulates, which if remaining in the blood stream can migrate in the pulmonary artery or one of its branches and cause harm. Filters may also be implanted prophylactically in pregnant women and/or morbidly obese patients going through a surgery to prevent thrombi or emboli from reaching the lungs and causing pulmonary embolism.